Protection against momentary loss of track circuit shunt



y 1956 A. HOOGERHYDE PROTECTION AGAINST MOMENTARY LOSS OF TRACK Filed Nov. 15, 1950 CIRCUIT SHUNT 2 Sheets-Sheet l FAA],

INVENTOR.

141:?! flooyerbyde BY HIS ATTORNEY United States Patent PROTECTION AGAINST MOMENTARY LOSS OF TRACK CIRCUIT SHUNT Arthur Hoogerhyde, Verona, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application November 13, 1950, Serial No. 195,236

Claims. (Cl. 246-41) My invention relates to protection against momentary loss of track circuit shunt. More particularly, my invention relates to apparatus for preventing false operation of railway trafiic controlling apparatus due to a momentary loss of track circuit shunt.

Track circuit control of railway traflic controlling apparatus such, for example, as signals and track switches isbased on the principle that when a train or other railway vehicle enters upon a track section, the rails of which are included in a track circuit in series with a track relay, a plurality of shunt paths, one through each pair of wheels and the associated axle, will be completed across the track circuit; and that such shunting of the track circuit will be effective to 'deenergize the track relay so that its front contacts will become opened and 'its back contacts will become closed, and will remain in that condition as long any any one of thepairs "of wheels remains on the track section. It has'been found, however, that under some conditions such, for example, as when the rails have become rusty or when there is some material such, for example, as sand on the rails, there may be a momentary loss of "shunt of the track circuit so that the track relay may become "energized and open its back contacts and'close its front contacts while 'one 'or more pairs of wheels remain 'on the track section.

A'railway signal for governing tra'ffic movements over such a track section, particularly if it is of a quick acting type such, for example, as a light signal, if controlled directly by a front contact of the track relay, might therefore display a proceed indication 'for a brief period of time during a momentary loss ofshunt of the track circuit. Obviously,"it would be a dangerous condition 'if a signal for a track section displayed a proceed indication for even a brief period-of time while the associated track section is occupied by'a car or train.

An object of my invention, therefore, is to provide protection against momentary loss of'track'circuitshunt, so'that a signal for governing traflic'movements 'over an associated track section will not be controlled to display a proceed indication, or some other trafiic controlling apparatus for the track section such, for example, as a track switch, will not be falsely operated because of a momentary loss of 'track circuit shunt.

A feature of my invention for attainingthis object is the provision ofa novel andimproved arrangement, embodying a repeater relay for a track relay, in whichthe repeater relay is retained in the'de'energized condition during a momentary loss of track circuit shunt, "and in which a traffic governing device such, for'e'xample, 'as a signal or a track switch is controlled "by the repeater relay instead of being controlled directly by the trajck relay.

I shall describe four forms of apparatus embodying my invention,'and shall then point out the novel features thereof in'claims.

In the accompanying drawings, Fig. l'is a diagrammatic view showing one form 'of apparatus embodying my 'inven'tion,-in which a direct current track circuit is employed; in which a first or back contact repeater relay TPB is controlled by aback contact of the track relay TR and is controlled to be slow releasing; in which a second or front contact repeater relay TP having a pickup winding '17 and a retaining winding 18 is controlled by the first repeater relay TPB andby a front-contact of the track relay TR and also by an energy storing device such, for example, as a'capacitor C and in which contacts of the second repeater relay TP are employed for controlling traffic controlling apparatus such, for example, as signals 18 and 28, instead of contacts of the track relay being employed for controlling the signals directly.

Fig. 2 is 'a diagrammatic View showing a modification of the apparatus of Fig. '1, also embodying my invention, in which the second repeater relay 'TP has only one control winding; and in which an asymmetric unit, designated-by'the reference character i, is provided in apickup circuit for the second repeater relay.

Fig. '3 is a diagrammatic'view showing another modification of the apparatus of Fig. 1, also embodying my invention, in which the second repeater relay TP has a hold-down magnetic shunt path as well as a pickup magnetic shunt path.

Fig. 4 is a diagrammatic view showing still another modification of the apparatus of 'Fig. '1, also embodying my'invention, in which an alternating current track circuit is employed'including the trackcontrol element of a two-element track relay ATR; in which a discharging circuit for a capacitor C is provided through a back contact of the track relay ATR; and in which a line control element h of a two-element track relay ATR has a pickup or energizing circuit controlled by a front contact 10 of relay TPB, and has a-stick or retaining circuit controlled by a front contact ll of relay ATR.

Similar reference characters refer to similar parts in each ofthe views.

Referring first to 'Fig. 1 of the drawings, a stretch of railway track is shown over which trains may normally move in either direction. 'Rails *1 and 1a of the stretch of 'trackare divided by insulated-joints 2 to form a track section T. Section T is provided with a track circuit which includes rails l-and 1a of thesectiomand asuitable source of current such, for example, as a battery 3 connectedacross the rails'adjacent one end of thesection, and also a'tra'ckrelay connected across the rails adjacent the opposite end of the section.

A signal, designated by'the reference character 18, is located adjacent one end a of section T for governing traflic movements over-section T toward the right, as shown in the drawing, which I shall assume is the eastbound direction. A second signal, designated by the reference character 28, is' located adjacent the opposite end b of section T forgovern'ing trafiic movements in the opposite or westbound direction oversection'T. Signals 1S and 28 maybe 'of any suitable design such, for eX- ample, as the well-known color light or searchlight'type.

A first, or back'contach'repeaterrelay, designated by the reference character TPB, is controlled by a back'contact of track relay TR. Relay T'PB is made 'slow releasingby a resistor, designatedby' the reference'character r, and a capacitor, 'designated'by the reference character 0, connected in'series with each other around the Winding of relay TPB. Relay-TPB is energized by current from a suitable source'such,"for example, as-abattery Q,'having apositive terminal Band-a negative terminal N.

Anenergy storing device, 's'hown-asa capacitor "and designated by the'reference character-C, is providedwith-a charging circuit which includes front points of contact 12 of relay TRand contacts'131and=14ofrelay TPB, and a'resistor *1r.

A'second, or front contact, repeater relay, designated by 'the'referencecharacterll, has a first and a-second control winding 17 and 18 which may be referred to as a pickup and a stick winding, respectively. The pickup Winding 17 may also be referred to as an energizing winding, and stick winding 18 may be referred to as a retaining winding.

A pickup or energizing circuit, which may also be referred to as an operating circuit, for relay TP, includes its winding 17 and is supplied with energizing current from capacitor C through a resistor 2r and through back points of contacts 13 and 14 of relay TPB. A stick or retaining circuit for relay TP includes its winding 18 and is supplied with energizing current from battery Q through a front contact of relay TR and a front contact of relay TP.

A circuit for controlling signal 18 to normally display a proceed indication includes a front contact 8 of relay TP. A circuit for controlling signal 28 to normally display a proceed indication similarly includes a front contact 9 of relay TP. 7

In Fig. 2, relay TP has only one control winding, and an asymmetric unit, designated by the reference character i, is connected in the pickup circuit for relay TP. Other portions of the arrangement shown in Fig. 2 are the same as are shown in Fig. 1.

In Fig. 3, relay TP has an electromagnet core structure which includes the usual core legs 4 and 5, and also includes an auxiliary core leg 6. Relay TP here has two magnetic flux paths, the first of which includes armature 7 in its picked-up position, as shown in the drawing, and the second of which includes armature 7 in its released or deenergized position. The first fiuX path, that is, in the picked-up position of armature 7, includes armature 7 and only legs 4 and 5 of the core of the electromagnet of relay TP. The second flux path, that is, in the deenergized position of armature 7, includes auxiliary core leg 6 in addition to the core legs 4 and 5 of relay TP.

In Fig. 3, the retaining circuit for relay TP includes control winding 10, on legs 4 and 5 of the core of relay TP, and the front point of contact 12 of relay TR. The pickup circuit for relay TP includes winding 11 on leg 6 of the core of relay TP, and the back points of contacts 13 and 14 of relay TPB.

When armature 7 is in its released position, winding 10 will produce in leg 6 of the relay core an electromagnetic flux which tends to hold armature 7 in the released position. Electromagnetic flux produced by winding 11 in the leg 6 is in the opposite direction and tends to cancel the flux in that leg produced by winding 10. As the flux produced by winding 11 builds up, a point will be reached where the combined downward pull of gravity and the flux produced by winding 10 will be counteracted, so that armature 7 will be picked up by the flux produced in the legs 4 and 5 of the relay core by winding 10 of relay TP. Armature 7 will then be retained in the picked-up position by the flux produced by winding 10, after capacitor C has been discharged.

In Fig. 4, alternating current is supplied by a suitable source such, for example, as an alternating current generator G, over a pair of line conductors or terminals designated by the reference characters BX and NX. The primary winding m of a track transformer designated by the reference character F is energized by current from terminals BX and NX. The line control element or winding h of a two-element alternating current track relay ATR is also energized by current from terminals BX and NX over contact 10 of relay TPB or contact 11 of relay ATR. The purpose of this control of winding h of relay ATR is to prevent a locked-out condition of relay TP in the event of a partial shunt of track section T which, on account of relay ATR being of an alternating current type, might cause contact 12 of relay ATR to become opened at its front point, deenergizing relay T P, and to then float for a brief period of time between its front and back points, and to then again become closed at its front point without becoming closed at its back point. If contact 12 of relay ATR did not become closed at its back point after becoming opened at its front point, and thereby deenergizing relay TP, relay TPB would not become energized, and relay TP would therefore remain deenergized after relay ATR again becameenergized.

The pickup circuit for relay TP which is here shown provided with a pickup winding 17 and a retaining winding 18, as in Fig. 1, includes'the front point of contact 16 of relay ATR as well as the back point of contact 13 of relay TPB.

A discharging circuit is shown for capacitor C through the back point of contact 16 of relay ATR. The purpose of this discharging circuit is to prevent a charge from becoming built up in capacitor C in the event of intermittent shunting of the track circuit.

Having described, in general, the arrangement and control of the various partsof apparatus embodying my invention, I shall now describe the circuits and operation in detail.

As shown in the drawings, all parts are in the normal condition, that is, track section T in Figs. 1, 2, and 3 is unoccupied, and therefore track relay TR is energized; track section T in Fig. 4 is also unoccupied, and therefore track relay ATR is energized; relay TP in each of the Figs. 1,2, 3, and 4 is energized by its retaining circuit; relay T PB is deenergized; capacitor C is in the discharged condition; and signals 18 and 28 are displaying a proceed indication.

The retaining circuit which is closed for relay TP in Fig. 1 passes from terminal B of battery Q, through the front point of contact 12 of relay TR, contact 15 of relay TP, and winding 18 of relay TP to terminal N of battery Q. Signal 18 is controlled to display the proceed indication by a circuit which includes contact 8 of relay TP. Signal 28 is similarly controlled to display a proceed indication by a circuit which includes contact 9 of relay TP. In Figs. 2 and 4, relay TP is energized by a retaining circuit which is similar to the circuit just traced for relay TP in Fig. 1. In Fig. 3, the circuit which is closed for retaining relay TP in the energized condition passes from terminal B, through the front point of contact 12 of relay TR, and winding 10 of relay TP to terminal N. In Fig. 4, the line control element h of relay ATR is energized by a stick or retaining circuit passing from terminal BX, through contact 11 of relay ATR, and control element h to terminal NX. Signals 1S and 28 in each of the Figs. 2, 3, and 4 are controlled to display a proceed indication as described in connection with Fig. 1.

I shall assume that, with apparatus embodying my invention, as shown in Fig. 1, an eastbound train passes signal 18 onto track section T, deenergizing relay TR.

With relay TR deenergized, the retaining circuit for re-' lay TP will be opened at the front point of contact 12 of relay TR, so that relay TP will be deenergized and will open the circuits for signals 18 and 28, causing signals 18 and 28 to cease displaying a proceed indication. With relay TR deenergized, relay TPB will become energized by a circuit passing from terminal B, through the back point of contact 12 of relay TR, the winding of relay TPB in multiple with a path through a resistor r and a capacitor c, to terminal N.

When the train leaves section T, relay TR will again become energized, thereupon opening the circuit for relay TPB at the back point of contact 12. Relay TPB is, however, slow releasing on account of resistor r and capacitor c being connected around its control winding, and therefore relay TPB will not at once release its contacts 13 and 14 from their front position. During the releaseperiod of relay TPB, while contacts .13 and 14 remain closed at their front points, capacitor C will become charged by a circuit passing from terminal B, through the front point of contact 12 of relay TR, front point of contact 13 of relay TPB, capacitor C, front point of contact 14 0f relay TPB, and resistor 1r to terminal N.

At the end of the release period of relay TPB, contacts 13 and 14 of relay TPB will become opened at their front. pointsand will: become closed. atctheirback points, thereby completing a pickupor operatingtcircuitvfor relay TP, this circuit passing from capacitor 'C, through the .back point of contact 13 of relay TPB, winding -17 of relay TP, terminal N, resistor 22', and the hack point of contact 14 of relay TPB, back to capacitorC. The release period for relay TPB. maybe of the. order of -15 seconds, during which capacitor C will become fully charged. Relay TP, upon becoming energized by its pickup circuit, completes its stick or retaining. circuit previou'sly'traced.

With relay TP again energized, the circuits previously described for controlling signals 15 andFZSto display a proceed indication will again be completed.

As I have already stated, relay TPB islmade slow releasing by resistor r and capacitor c connected in series with each other around the winding of relay TPB. The values of resistor r and capacitor may be selected so that the release time of relay TPB may, for example, be of the order of 15 seconds.

The purpose of capacitor C is to'check'that the release time ofrelay TPBtis maintained at a suitable length such, for example, as l'seconds. Thevaluesof resistor 11' and capacitor C may be'selected so' that capacitor C will not become sufliciently charged to pickup relay 'TP if relay TPB releases too quickly. If, forexample, capacitor 0 becomes disconnected from relay TPBso that relay TPB releases quickly, capacitor C would not become sufficiently charged to pick up relay TP. "Therefore, it will be seen that the circuit-which'includes resistor 1r and capacitor C checks that the release-time of relay T PB is sufliciently long for the picking up of relay'TP to bridge over any momentary-loss of 'shunt dfthe track circuit for section T.

'1 shall now assume-that, with-apparatus-arranged as shown in Fig. 1, an eastbound train enterssection T, deenergizing relay TRand thereby causing relay TPB to'become-energized as previously'described. I shallassume further that there is-a momentary loss-of shunt of the track circuit for section T, so that relay'IRpicks up for a brief period of time opening theenergizingz-circuif-for relay TPB, which, however, doesi-notimmediatelyirelease 'due to its slow. release characteristic.

The charging circuit for "capacitor C will therefore become closed, as previously traced-but will-become opened by relay TR before relay TPB releasesitsrcontacts 13 and 1410 their back points. Relay TPB will then.:again' become'energized by its circuit :which includes the back point of contact 12 of'relay .TR. Contacts 13 and 140i relay TPB will thereforestill'not berreleasedto their back points, but will be retained closed ,-at:.their.front;points. The energizing circuit for relay TP, which includes the back points of contacts 13and :14 of:relay-TPB, will-therefore not become'closed to effect-operation of relay TP for closing its front contacts, and therefore the circuits for signals 18 and 28 will remain open at-contactsi8 and 9, respectively, of relay TP, .so that signals :1Sand 28 will not be controlled to display a proceed indication.

It follows that, in apparatus embodying my invention, relay TP remains deenergized during a momentary loss of shunt of the'track circuit for section -T, 'sothat signals 18 and 28 will not display ,a proceed indication. Apparatus embodying my inventiontherefore providesprotection against=false operation ofrailwaytrafiic controlling apparatus such, for example, as arailwayisignal, during amornentary loss of shunt of a track .circuitover which the signals govern traffic movements.

In the form of apparatus shown inFig. 2, only one control winding is provided for relay TI. The pickup circuit for relay TP here includes an asymmetric .unit i, but is otherwise the same asin Fig. 1. Allotherportions of the circuits and apparatus of Fig.2 arethesame as in Fig. 1. The purpose of the asymmetric unit i is toprevent capacitor 'C from becoming charged through the stick 'or retainingcircuit for relay IF.

I shall next assume that, with apparatus embodying my invention as shown in Fig. '3, an eastbound train enters section 'T, deenergizing relay -TR, whichinturn' opens the retaining'circuitfor-relay TP, causing relay TP-to become deenergized. With relay TP deenergized, the circuits for controlling signals IS'and 28 to display aproceed indication will'become opened-at contacts -8 and-9, respectively, of relay TP, so-that signals 18 and 25' will cease to display a proceed indication. With relay TR "deenergized, relay TPB will become energized -by its circuit which is similar to the circuit previously traced for relay TPB in 'Fig. 1.

When the train leaves track section T, relay TR will again become energized, thereby completing the retaining circuitpreviously traced for relay TP. With armature 7 of relay TP in its released or'deenergized position, the fiux produced in leg 6 of the relay core bywinding 10 of relay TP will tend'to hold armature 7 down, sothat contacts 3 and"9 of relay TP will remain open. With relay TR energized, a circuit will be completed for charging capacitor C, which is similar to thecircuit-previously traced for charging capacitor C in Fig. 1.

At the end of the release period of relay TPB, contacts 13 and 14 of relay TPB willbecome closed'at their back points, thereby completing a circuit for energizing'winding-11 of relay TP, this circuit passing from capacitor C, through the back point of contact 13 of relay TPB, winding 11 of relay TP, terminal N, resistor Zr and the back .pointof contact 14 of relay TPB back to capacitor C. When the flux produced by winding '11, which is in opposition to-the'flux produced 'by winding 10, has built-up :sufliciently, 'it will counteract the downward force of gravityand of the-flux produced by winding 10,so that the upwardpull of the fluxproduced by winding '10 will then move armature '7 from its releasedposition to its picked-up position. ContactsS and 9 of relay TP will therefore again-be closed, 'so that signals 1S and 28, respectively, will again display a proceed indication.

Inthe event of'a momentary loss of 'shunt of the track circuitfor section T While itzis occupied by a train, the circuit-for winding '10 of relay TP-and the charging circuit for capacitorC-will again become closed, as previously described. Relay TR will, however, again release its contact '12, so that the circuit for chargingcapacitor- C willbecorne opened and thecircuit for energizing relay TPB will again become closed at the'back point of contact :12 of relay TR,before contacts 13 and 14 of relay T PB havebecome closed at their back points for completing theenergizing circuit for control winding 11 ofrelay TP. Relay TP will therefore remain deenergized,-so that the circuits for controlling signals 15 and 28 to display a proceed indication will remain open at contacts 8 and 9, respectively, and signals 1Sand 28 will therefore not be controlled todisplay a proceed indication.

I shall now assume that, with apparatus embodying my invention as shown in Fig. 4, a train passes signal 15 onto section T, deenergizing relay ATR. The retaining circuit for relay TP will .thereforein turn become opened at .the front point of contact 12 of relay ATR, so that relay T? will become deenergized. With relay TP deenergized, contacts 8 and 9 of this relay will become opened, thereby causing signals 13 and 2.8 to cease to display a proceed indication. With relay ATR deenergized, relay TPB will become energized by a circuit similar to the circuit traced-forrelay TPB in .Fig. 1.

With relay TPB energized, a pickup circuit will be closed for winding h of relay ATR, this circuit passing from terminal BX, through contact 10 of relay TPB,and winding h to terminal NX. Relay ATR will, however, not become operated, as long as track section T is occupied by the train.

With relay ATR deenergized, a discharging-circuit is completed for capacitor C, this circuit passing fromcapacitor 0, through resistor 4r, back point of contact 16 of relay ATR, and terminal N back to capacitor-C. charge which has remained in capacitor'C at -the time pated.

relay ATR becomes deenergized will therefore be dissipreviously traced through contact 11 of relay ATR.

During the period from the time contact 12 of relay ATR becomes closed at its front point until contact 13 of relay TPB becomes opened at its front point, a circuit will be closed for charging capacitor C, this circuit passing from terminal B, through the front point of contact 12 of relay ATR, front point of contact 13 of relay TPB, front point of contact 16 of relay ATR, resistor 41', and capacitor C to terminal N.

At the end of the release period for relay TPB, contact 13 of relay TPB will become closed at its back point, thereby completing a pickup circuit for relay TP, this circuit passing from capacitor C, through resistor 4r,

from point of contact 16 of relay ATR, back point of contact 13 of relay TPB, winding 17 of relay TP, and

terminal N, back to capacitor C. Relay TP, upon thus becoming energized, will again complete its stick circuit previously described. With relay TP energized, its contacts 8 and 9 will again complete circuits for controlling signals 13 and 25, respectively, to display a proceed indication.

In the event of a momentary loss of shunt While track section T is occupied by a train, relay ATR will close its contact 12 at the front point for again completing a charging circuit for capacitor C, but contact 12 of this relay will again become opened at its front point before the end of the release period for relay TPB, so that contact 13 of relay TPB will remain closed at its front point, and the pickup circuit for relay T? which includes the back point of contact 13 of relay TPB will not become closed for operating relay TP. With relay TP remaining deenergized, contacts 8 and 9 of this relay will therefore not complete the circuits for controlling signals 18 and 28, respectively, to display the proceed indication.

I shall assume further that, with apparatus as shown in Fig. 4, there are several intermittent losses of shunt of the track circuit for section T, in succession. Each time that relay ATR picks up, the circuit for charging capacitor C becomes closed, so that capacitor C becomes partly charged. Each time that relay ATR becomes released,

however, capacitor C will become discharged by the circuit which includes the back point of contact 16 of relay ATR. The purpose of discharging capacitor C at the time when track relay ATR becomes deenergized, is that, without this provision, a charge could be built up in capacitor C by repeated momentary losses of shunt, and if capacitor should become disconnected from relay TPB, permitting relay T PB to release quickly, relay TP might become energized quickly, so that signals and 28 would be controlled to display a proceed indication during a momentary loss of shunt.

Although I have herein shown and described only a few forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention. what I claim is:

1. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also-said source of current, a first repeater relay arranged to be slow releasing, means controlled by a back contact of said track relay for energizing said first repeater relay, an energy storing device, means controlled by a front contact of said track relay and by a front contact of said first repeater relay for charging said energy storing device, a second repeater relay, a pickup circuit including said energy storing device and a back contact of said first repeater relay for energizing said second repeater relay, a stick circuit controlled by a front 8 contact of said track relayfor retaining said second repeater relay in the energized condition, and trafiic controlling apparatus controlled by a front contact of said second repeater relay.

2. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including'the rails of said section and said track relay and also said source of current, a first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, an energy storing device, means including a front contact of said track relay and a front contact of said first repeater relay for charging said energy storing device, a second repeater relay, a pickup circuit including said energy storing device and a back contactof said first repeater relay for energizing said second repeater relay, a stick circuit controlled by a front contact of said track relay for retaining said. second repeater relay in theenergized condition, and trafiic controlling apparatus controlled by a front contact of said second repeater relay.

3. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay, means including a back contact of said first repeater relay for efiecting energization of said second repeater relay, means including a front contact of said track relay for retaining said second repeater relay in the energized condition, and tratfic controlling means including said second repeater relay.

4. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay having a first and a second control winding, means including a back contact of said first repeater relay for effecting energization of said first control winding of said second repeater relay, means including a front contact of said track relay for energizing said second control winding of said second repeater relay, and trafiic controlling means including said second repeater relay.

5. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay, an asymmetic unit, means including said asymmetric unit in its low resistance direction and including a back contact of said first repeater relay for effecting energization of said second repeater relay, means including a front contact of said track relay for retaining said second repeater relay in the energized condition, and traflic controlling means including said second repeater relay.

6. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay having 'a first and a second control winding and having an armature and a front pole piece and also a back pole piece, means including a back contact of said first repeater relay for effecting energization of said first control winding of said second repeater relay for sending magnetic flux in a given direction through said armature and said back pole piece, means including a front contact of said track relay for energizing said second control Winding of said second repeater relay for sending magnetic flux in the opposite direction through said armature for opposing the magnetic flux in said given direction for raising said armature from said back pole piece to said front pole piece and retaining said armature in the raised position, and traffic controlling means including said second repeater relay.

7. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay, an energy storing device, means including front contacts of said track relay and said first repeater relay for charging said energy storing device, pickup circuit means for said second repeater relay including said energy storing device and a back contact of said first repeater relay, retaining circuit means for said second repeater relay including a front contact of said track relay, and traffic governing means controlled by means including said second repeater relay.

8. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and said track relay and also said source of current, a slow releasing first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, an energy storing device, means including a front contact of said first repeater relay for charging said energy storing device, a second repeater relay, means including said energy storing device and a back contact of said first repeater relay and also a front contact of said track relay for efiecting energization of said second repeater relay, means including a front contact of said track relay for then retaining said second repeater relay in the energized condition, means controlled by a back contact of said track relay for discharging said energy storing device, trafiic governing means, and means including said second repeater relay for controlling said traffic governing means.

9. In combination, a section of railway track, a track relay having a track control element and a line control element both of which must be energized to elfect operation of said track relay to close its front contacts, a source of current, a track circuit for said section including the rails of said section and said track control element of said track relay and also said source of current,

a slow releasing first repeater relay, means including a front contact of said first repeater relay for energizing said line control element of said track relay, means including a front contact of said track relay for retaining said line control element energized, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay, means including a back contact of said first repeater relay for effecting energization of said second repeater relay, means including a front contact of said track relay for retaining said second repeater relay in the energized condition, and trafiic controlling means including said second repeater relay.

10. In combination, a section of railway track, a track relay, a source of current, a track circuit for said section including the rails of said section and a control element of said track relay and also said source of current, a slow releasing first repeater relay, means including a front contact of said first repeater relay for effecting operation of said track relay for closing its front contacts only if said front contact of said first repeater relay is closed and said track circuit is energized, means including a back contact of said track relay for energizing said first repeater relay, a second repeater relay, means including a back contact of said first repeater relay for efiecting energization of said second repeater relay, means including a front contact of said track relay for retaining said second repeater relay in the energized condition, and trafiic controlling means including said second repeater relay.

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